In a blender or food processor, combine orange juice, apple cider vinegar, honey, Dijon mustard, minced garlic, orange zest, salt, pepper, oregano, and red pepper flakes if using. Blend until smooth.

With the motor running, slowly drizzle in the olive oil through the top opening in a thin, steady stream until the vinaigrette is creamy and emulsified.

Taste and adjust seasoning to your liking. Set aside 1 1/4 cups of the vinaigrette for the chicken marinade and refrigerate the remaining 1 1/4 cups to use later for the salad.

In a large bowl, whisk together the reserved 1 1/4 cups vinaigrette with the additional 2 tablespoons orange juice, 2 tablespoons Dijon mustard, 1 tablespoon honey, 1 teaspoon salt, 1/2 teaspoon pepper, 1 teaspoon oregano, and optional red pepper flakes.

Add the chicken breasts and turn to coat evenly. Let marinate at room temperature for 15-20 minutes; do not exceed 1 hour to avoid toughening the meat.

Remove the chicken from the marinade, letting excess drip off, and discard the used marinade.

Preheat a grill, grill pan, or large skillet over medium heat.

Place the chicken in a single layer on the grill and cook for 6-8 minutes per side, until an instant-read thermometer inserted into the thickest part reads 165°F. Transfer to a cutting board and let rest for 10 minutes before slicing or cubing.

While the chicken rests, rub the corn with olive oil and season with salt and pepper. Grill over medium-high heat, turning every 1 1/2 to 2 minutes, until charred on all sides (about 8 minutes total). Let cool, then cut the kernels off the cob.

In a large bowl, toss the chopped romaine with about 1/4 cup of the reserved vinaigrette until evenly coated.

Divide the dressed lettuce among 4-6 plates or place in a large serving bowl.

Top the lettuce with sliced or cubed grilled chicken, grilled corn kernels, red onion slices, cucumber slices, cherry tomatoes, and diced avocado.

Drizzle the remaining vinaigrette over the salad and serve immediately.